Wednesday, November 15, 2006

Sodium-Affected Soil Landscapes in Western North Dakota (MLRA 54).

Jimmie Richardson, Douglas Wysocki, Michael Ulmer, and Thomas Champa. USDA-NRCS, Mail Stop 34, 1000 Centennial Mall North, Room 152, Lincoln, NE 68508

Sodium-affected soils have widespread occurrence in arid and semi arid regions including western ND. Such soils pose significant agricultural management problems and can be an environmental concern. Hence, it is important to understand both the distribution and genesis of sodium-affected soils.  Our main objective is to integrate four factors that largely control distribution of sodium-affected soils into a soil landscape model. The factors are parent rock salt content, slope development, management history, and soil hydrology. Sodium in these landscapes originates from the parent rock. Sodium distribution, however, is controlled by hillslope development, amount and timing of precipitation, and landscape focused hydrology. Large erosional footslopes dominate western ND soil landscapes and are a geomorphic mechanism for near surface hydrology. Precipitation that enters the soil flows laterally in lower soil horizons and/or upper bedrock zones. At lower footslope positions, soil water nears the surface and dissolved salts (sodium) are concentrated by evaporative discharge. We explain this process using graphic, cross sectional models that relate soil patterns to hillslope position and seasonal hydrodynamics.